Rotary drillholes were advanced at the base of the cable percussion holes to recover continuous rock core samples and to provide information on the mine working situation.
Cable percussion boreholes weere advanced through the superficial deposits to obtain representative samples of the soils encountered.
Machine excavated trial trenches were used to assist in determining the extent of previous landfilling.
Static cone penetrometer testing was used in certain areas to yield in-situ parameter information relating to the ground sequence.
|Intrusive Site Work||53 No. the cable percussive boreholes were advanced into a variable thickness and consistency of superficial cohesive strata (to a maximum depth of 32mBGL), the majority of which were followed by rotary methods into the shallow underlying bedrock (to 36.90mBGL). A coal authority permit was acquired for drilling in areas of known coal seams. In-situ SPT and hand shear vane testing was conducted at specified intervals. The primary purpose was to determine the depth of bedrock including the identification of shallow coal seams. This was to inform foundation design at depth and design of cuttings, embankments and foundations over open cast fill. During drilling, ground gas monitoring was performed as a precautionary measure to assess for noxious/flammable gas and all plant was fitted with spark arrestors. Clean drilling technologies were employed to prevent the downward migration of contaminants. |
104 No. the mechanically excavated trial pits were scheduled to inform carriageway, shallow foundations, earthworks and drainage network elements as well as various geotechnical requirements through soakaway and in-situ testing for soil strength parameters.
16 No. trial trenches were used to delineate extents of infilled ground and soft ground (alluvium) within the scheme.
|Geology||The ground conditions in the vicinity of the proposed road corridor were indicated to principally relate to glacial till (predominantly fine grained (cohesive) with silty/granular inclusions)) overlain by patchy near surface alluvium (in connection with localised surface water channels that intersect the scheme. A limited occurrence of made ground (fill) of varying composition and thickness - typically including reworked locally derived superficial deposits/demolition waste/opencast backfill was also proven within places associated with previous mining or developmental interactions. The solid regional geology relates to the Millstone Grit Formation (principally sandstone) evidently weathered intermittently at its upper interface and the Pennine Lower Coal Measures Formation which presented a risk of known/unrecorded mine workings at the southern extent of the site.|
|Miscellaneous||Disturbed/undisturbed sampling techniques.
Hand penetrometer testing.
Field screening of selected environmental soil samples using PID methods to determine SVOC/VOC levels.
Variable/ constant head permeability testing.
Post-works groundwater and gas monitoring in installations over a three month period.
Surveying of all investigation positions.
The proposed scheme comprises a major new orbital road on the north-eastern fringe of Leeds city centre that will serve as a connection between the A6120 outer ring road, near Roundhay Park and Manston Lane (at the southern limit). The intended dual carriageway layout will span over an approximate route of 7km and encroach open undeveloped and agricultural land, commercial-use, infrastructure (including A64 and A58) and natural water features. The project forms part of the East Leeds Extension (ELE) (under the local planning regime of Leeds City Council) involving the redevelopment of 233 hectares of land allocated for residential housing subject to statutory approval and land purchase.
Atkins Ground Engineering were appointed by Balfour Beatty (the Principle Designer for the project) within the role of Investigation Supervisor to implement (in partnership) the detailed design phase of the scheme and were present on site throughout the intrusive works. This study supplements the main ground investigation works performed by Mouchel (in 2015/16).
The initial pre-contract stage involved ensuring that all health and safety information was in place, with Allied Exploration assuming the role of Principal Contractor for the scheme. Detailed Risk Assessments and Method Statements were developed, including a detailed plan illustrating the sequence of the works. Landowners were liaised with to approve access ways and a pre-condition survey was also undertaken in advance of the intrusive works.
Four cable percussive rigs, three rotary drill units, one subcontracted CPT machine and a contigent of full-time engineers for trial pitting and/or working within the capacity of a supervisory role for delivery of the contract, were allocated to the site.